The present invention relates generally to a refrigerator. More particularly, the present invention relates to a “bottom freezer” type refrigerator having a sub-compartment on the door for the top mounted fresh food compartment.
Generally, a refrigerator includes a freezer compartment and a fresh food compartment which are partitioned from each other to store various foods at low temperatures in appropriate states for a relatively long time.
It is now common practice in the art of refrigerators to provide an automatic icemaker. In a “side-by-side” type refrigerator where the freezer compartment is arranged to the side of the fresh food compartment, the icemaker is usually disposed in the freezer compartment, and ice is delivered through an opening on the door for the freezer compartment. In this arrangement, ice is formed by freezing water with cold air in the freezer compartment, the air being made cold by the refrigeration system of the refrigerator, which includes an evaporator disposed in the freezer compartment.
In a “bottom freezer” type refrigerator where the freezer compartment is arranged below or beneath a top mounted fresh food compartment, convenience necessitates that the icemaker is disposed in a thermally insulated sub-compartment mounted on the door for the top mounted fresh food compartment, and ice is delivered through an opening on the door for the fresh food compartment. In such an arrangement provision must be made for providing adequate cooling to the sub-compartment to enable the icemaker to form ice and for the ice to be stored.
In one approach, the cold air in the freezer compartment is used to cool the icemaker. More specifically, the cold air in the freezer compartment, preferably the cold air around the evaporator in the freezer compartment, is circulated through the sub-compartment via a duct loop to maintain the icemaker in the sub-compartment at a temperature below the freezing point of water during operation. In this arrangement, a substantial portion of the duct loop is embedded in the insulation material of the sidewall of the main body of the refrigerator. The duct itself needs to have a sufficiently large cross-section to ensure that a sufficient amount of cold air can be delivered to and from the sub-compartment. However, the duct sometimes adversely reduces the thickness of the insulation material so that multiple heaters are needed in order to prevent the formation of condensation on the external surface of the main body. Using the heaters increases the energy consumption of the refrigerator. In addition, both the heaters and the duct loop increase the manufacturing cost.
In another approach, a liquid coolant in the nature of a mixture of propylene glycol and water is used to cool the icemaker. The liquid coolant is cooled by the cold air in the freezer compartment, and then is circulated to and from the icemaker in the sub-compartment through a circulation loop by a pump. The circulation loop needs to be liquid-tight. This is especially true with respect to the section of the circulation loop that extends between the main body of the refrigerator and the sub-compartment on the door for the fresh food compartment. This approach provides good cooling results, but it complicates the maintenance and/or repair process when the door for the fresh food compartment needs to be removed from the main body of the refrigerator.
In either approach, the working medium, be it chilled air or a liquid coolant, has to be delivered into, and removed from the sub-compartment.